1. Field of the Invention
The present invention relates to a lower tool device for a press brake, and more specifically to a lower tool device by which a lower tool can be replaced easily in a lower table.
2. Description of the Prior Art
As is well known, a press brake is provided with an upper table (which may be referred to as an upper apron) and a lower table (which may be referred to as a lower apron) arranged in such a way as to be opposed to each other, and further with a ram for moving either of the upper or lower table up and down.
To bend a plate like workpiece for instance, an upper tool is mounted on the lower part of the upper table, and a lower tool is mounted on the upper part of the lower table. Therefore, when the movable side table is moved up and down so that the upper and lower tools can engage with each other, a workpiece positioned between the upper and lower tools is bent.
In the prior art lower tool holder, as shown in FIG. 7, a tool holder block 705 is mounted on a base plate 703 mounted on the upper portion of a lower table 701 of a press brake. Further, a roughly T-shaped slot 707 is formed extending in the front and rear direction in the tool holder block 705 or between two adjacent tool holder blocks 705 arranged horizontally.
Further, a fastening bolt 711 is provided vertically on the under surface of the lower tool 709 from below, and further a washer member 713 is attached to this fastening bolt 711. A flange portion 705F Of the tool holder block 705 is fastened by the fastening bolt 711 and the washer member 713 provided in the slot 707.
In other words, conventionally, the lower tool 709 is fastened to or loosened from the tool holder block 705 by fastening or loosening the fastening bolt 711 relative to the tool holder block 705.
In the prior art structure, although the structure of fastening the tool 709 to the tool holder block 705 is simple, a number of fastening bolts 711 are arranged in the longitudinal direction of the tool 709, and therefore it is necessary to fasten or loosen the number of fastening bolts 711 by inserting a tool (e.g., a spanner) into a narrow slot 707, thus causing a problem in that the tool exchanging work is extremely troublesome.